KR20220052926A - Method for making organic carbonates - Google Patents

Abstract

The present invention relates to a process for preparing an organic carbonate, comprising the step of contacting carbon dioxide with an alcohol in the presence of water and a catalyst in a reaction zone to produce the organic carbonate, wherein the organic carbonate is continuously discharged from the reaction zone. is removed with

Description

Method for making organic carbonates

The present invention relates to a process for preparing organic carbonates.

Organic carbonates such as dialkyl carbonates, diaryl carbonates and alkylene carbonates are widely used in the chemical industry. Because of their low toxicity, organic carbonates are widely used as solvents and as monomers for polymer production and many other uses. The use of carbonates as monomers to form polymers may expand, greatly increasing their demand in the global market. Organic carbonates are important precursors for the production of polycarbonates, polyesters, polyurethanes and polyamides. In addition, organic carbonates can be used as intermediates for chemical alcohol purification or medical or cosmetic applications, or as high-k component for lithium batteries or as entrainers for separation or as solvent or fuel oxygenate additives.

Since current and existing synthetic techniques are characterized by the use of phosgene as a building block, which is banned in several countries, the development of new methodologies for the synthesis of organic carbonates has attracted much attention worldwide. The phosgene-free synthesis of organic carbonates such as dimethyl carbonate (DMC) and diethyl carbonate (DEC) is receiving a lot of attention. There is a continuing need to develop improved processes for preparing organic carbonates. It is an object of the present invention to provide a technologically advantageous, efficient and inexpensive process for preparing organic carbonates.

Surprisingly, it has been found that the process for preparing organic carbonate as described above is provided as a process wherein carbon dioxide is contacted with an alcohol in the presence of water and a catalyst in a reaction zone to produce the organic carbonate, wherein the organic carbonate is continuously removed from the reaction zone became

Accordingly, the present invention relates to a process for preparing an organic carbonate, comprising the step of contacting carbon dioxide with an alcohol in the presence of water and a catalyst in a reaction zone to produce said organic carbonate, wherein said organic carbonate is produced in said reaction zone are continuously removed from

It is known to prepare the organic carbonate by reacting an alcohol and carbon dioxide in the presence of a catalyst to prepare an organic carbonate and water. A literature overview of this type of reaction is provided in "Conversion of CO ₂ to Valuable Chemicals: Organic Carbonate as Green" by T. Tabanelli et al. in Chapter 7 Section 3.2 of "Studies in Surface Science and Catalysis", volume 178, 2019, Elsevier BV. Candidates for the Replacement of Noxious Reactants". In the above overview, it is recognized that the CO ₂ direct condensation reaction with alcohols and diols suffers from several obstacles associated with the unfavorable thermodynamic equilibrium for the reaction. It is stated in the above outline that the continuous removal of water from the reaction medium will shift the unfavorable equilibrium towards the products. A solution according to the above outline is the use of effective dehydrating agents. However, the continuous removal of the organic carbonate product required in the present invention is not disclosed or suggested in the above outline.

1 shows an embodiment of the present invention.

Although the process of the present invention and the stream or composition used in the process may be described as "comprising, including" or "containing" one or more of the various described steps and components, respectively, They may also be “consist essentially of” or “consist of” one or more of the various described steps and components, respectively, above.

In the context of the present invention, if a stream or composition comprises two or more components, these components should be selected in total amounts not exceeding 100%.

Also, where upper and lower limits are recited for a property, the range of values defined by the combination of any of the upper and lower limits is also implied.

In the examples and examples that follow, the location of the different feed streams to the distillation column and the location of the product streams from the distillation column are selected so that the components are directed where they are required by their relative volatility. This means that different alcohol reactants and different organic carbonate products can lead to different feed locations to drive chemical and separation processes.

In the present invention, carbon dioxide is contacted with alcohol in the presence of water and a catalyst in a reaction zone to prepare an organic carbonate. With respect to dimethyl carbonate as the target organic carbonate, the overall reaction is described below:

CO ₂ + 2 CH ₃ OH ↔ (CH ₃ O) ₂ C=O + H ₂ O

This carboxylation of alcohols has limitations due to thermodynamics. It has an unfavorable equilibrium for the products organic carbonate and water. However, in the present invention, since the organic carbonate is continuously removed from the reaction zone, the thermodynamic equilibrium is favorably shifted towards the product. In addition, in the present invention, water must additionally be present in addition to the catalyst, and this water may be supplied as further described below. Therefore, in the present invention, molecular sieves or dehydrating agents such as sodium or magnesium sulfate are not used as in the above literature summary.

Also advantageously, the present invention relates to a process starting from an alcohol feed stream containing carbon dioxide (eg, taken from flue gas) and (bio)ethanol which may originate, for example, from fermentation and generally water. Allows for the direct synthesis of organic carbonates. Since water is required in the present invention anyway, advantageously, the water does not need to be separated from the alcohol prior to use in the present invention.

Accordingly, in the present invention, the organic carbonate is continuously removed from the reaction zone. The process is preferably a continuous process. Preferably, this continuous removal of the organic carbonate is achieved by carrying out the reaction in a distillation column. As used herein, "distillation column" refers to a column in which distillation is performed, wherein the distillation is a method of separating the components from a liquid mixture of components by using selective boiling and condensation, wherein a portion of the condensed liquid is It may or may not be recycled (refluxed) to the column.

In this way, advantageously, the production and separation of the organic carbonate are carried out simultaneously in the distillation column, thereby shifting the thermodynamic equilibrium towards the product as well to produce more organic carbonate. Accordingly, it is preferred that the reaction zone is part of a distillation column and that the organic carbonate is continuously removed from the distillation column. Such distillation columns are also referred to as "reactive distillation columns".

In the present invention, it is preferred that carbon dioxide, the alcohol and water are supplied to the reaction zone. They may be supplied individually and/or together. For example, the alcohol and water may be fed to the reaction zone together. The amount of water fed to the reaction zone is, based on the total amount of water and alcohol fed to the reaction zone, from 1 to 99% by weight, preferably from 5 to 95% by weight, more preferably from 10 to 80% by weight, most Preferably, it may be 20 to 50% by weight. The presence of water in the process can have various advantages. First, as further described below, water is a polar reaction medium suitable for the intended reaction in which carbon dioxide can be dissolved. Second, as further described below, water may aid in any further purification of a stream comprising carbon dioxide, water, alcohols and organic carbonates. Third, as further described below, water may be required to activate and stabilize the catalyst used in the process.

Carbon dioxide is preferably supplied to the reaction zone in such an amount that the aqueous liquid phase present in the reaction zone is saturated with dissolved carbon dioxide. This dissolved carbon dioxide may also be referred to as “liquid” carbon dioxide.

In the present invention, carbon dioxide is contacted with an alcohol in the presence of water and a catalyst in a reaction zone of a first distillation column to produce a mixture comprising carbon dioxide, water, alcohol and organic carbonate, wherein the organic carbonate is separated from the first distillation column It is preferred that the bottom stream is continuously removed from the first distillation column, and the top stream from the first distillation column comprises carbon dioxide, water, alcohol and optionally organic carbonate. The organic carbonate may be present in the overhead stream as it may form an azeotrope with water. For example, it is known that dialkyl carbonates form azeotropes with water whereas alkylene carbonates do not. Thus, when the organic carbonate is a dialkyl carbonate, it is present in both the bottom stream and the top stream.

As used herein, "top stream" or "bottom stream" from a column means from 0% to 30%, more suitably from 0% to 30%, more suitably, from the top of the column or the bottom of the column, based on the total column length, respectively. 20%, more suitably 0% to 10%, refers to the stream exiting the column.

Fresh water is preferably fed to the first distillation column at a position higher than the position at which fresh alcohol is fed, preferably at or above the reaction zone. In addition, it is preferred that fresh alcohol is fed to the first distillation column at a position lower than the position where fresh water is supplied, preferably at a position lower or lower than the reaction zone. The reaction zone may be a zone in the first distillation column comprising a packing containing a heterogeneous catalyst, for example a structured packing. "Fresh" water or alcohol refers to water or alcohol that has not been recycled. Alternatively or additionally, fresh water and fresh alcohol may be fed together as part of the aqueous alcohol stream, preferably at a location below or below the reaction zone. In addition, the carbon dioxide is preferably supplied at a position lower than the position at which fresh alcohol is supplied. An inert gas such as nitrogen may be supplied together with the carbon dioxide. Also, carbon dioxide may be supplied with water. Advantageously, water does not need to be removed from the feed stream comprising both carbon dioxide and water, since in any case water is needed in the process, in particular to dissolve said carbon dioxide as described above. In the present invention, a stream comprising 5 to 100% by weight of carbon dioxide and the remainder comprising inert gas and/or water may be fed.

When the aforementioned overhead stream from the first distillation column comprises carbon dioxide, water, alcohol and organic carbonate, the overhead stream comprises a gas stream comprising carbon dioxide, a first liquid stream comprising organic carbonate and alcohol and an alcohol. and at least partially condensed and separated into a second liquid stream comprising water. The latter separation can be performed by using a decanter. The separated stream comprising carbon dioxide may be removed from the process or recycled to the first distillation column. The separated stream comprising organic carbonate and alcohol may be recycled to the first distillation column so that additional organic carbonate may be recovered and the alcohol recycled to the reaction zone. It is also preferred that the stream is fed to the first distillation column at a position lower than the bottom of the reaction zone and lower than a position where fresh alcohol is fed. The separated stream comprising alcohol and water may be fed to a second distillation column in which separation into a stream comprising alcohol and a stream comprising water is performed. The separated stream comprising alcohol from the second distillation column may be recycled to the first distillation column. The stream may be fed to the first distillation column individually or together with fresh alcohol. A separated stream comprising water from the second distillation column may be removed from the process.

Preferably, the temperature of the reaction zone is between 50 and 200 °C, more preferably between 60 and 160 °C and most preferably between 70 and 140 °C. Also preferably, the pressure in the reaction zone is from 5 mbar to 10 bar, more preferably from 10 mbar to 5 bar. The pressure can be selected and set such that the desired boiling temperature of the reaction zone is realized.

In the present invention, the alcohol may be an aromatic C ₅ -C ₉ alcohol and/or an aliphatic C ₁ -C ₃₀ alcohol. The aromatic C ₅ -C ₉ alcohol may be phenol. Preferably, in the present invention, the alcohol is an aliphatic C ₁ -C ₃₀ alcohol. Preferably, the aliphatic C ₁ -C ₃₀ alcohol has 1 to 10 carbon atoms, more preferably 1 to 5 carbon atoms and most preferably 1 to 3 carbon atoms. Also preferably, the aliphatic C ₁ -C ₃₀ alcohol is selected from methanol, ethanol and isopropanol, more preferably methanol and ethanol, most preferably ethanol.

Further, in the present invention, the alcohol may contain one hydroxyl group (monohydric alcohol) or two or more hydroxyl groups (polyhydric alcohol). In the case of monohydric alcohols, linear organic carbonates are formed, which may be dialkyl carbonates (if the starting alcohol is aliphatic) or diaryl carbonates (if the starting alcohol is aromatic). In the case of polyhydric alcohols, two of the hydroxyl groups, in particular two hydroxyl groups separated from each other by two or three carbon atoms, can react with carbon dioxide to form a cyclic organic carbonate. Examples of such polyhydric alcohols are monoalkylene glycols such as monoethylene glycol or monopropylene glycol, which, when reacted with carbon dioxide, form alkylene carbonates such as ethylene carbonate and propylene carbonate. Another example of such a polyhydric alcohol is glycerol, which forms glycerol carbonate when reacted with carbon dioxide.

As described above, in the present process, both aromatic C ₅ -C ₉ alcohols and aliphatic C ₁ -C ₃₀ alcohols may be fed. This has the advantage that dialkyl carbonates and alkyl aryl carbonates that can be disproportionated to diaryl carbonates can be formed. For example, when a mixture of methanol and phenol is used in the process, dimethyl carbonate and methyl phenyl carbonate may be formed. This disproportionation of the methyl phenyl carbonate will then produce diphenyl carbonate and further dimethyl carbonate.

In the present invention, a catalyst must be used. Any catalyst that catalyzes the formation of organic carbonates from carbon dioxide and alcohols can be used.

The catalyst is preferably an acid catalyst. In addition, it may be preferable that the catalyst is a basic catalyst. In general, catalysts having both acidic and basic properties can be used. Accordingly, in the present invention, the catalyst may be acidic or basic, or may have acidic and basic properties. Also preferably, the catalyst is a heterogeneous catalyst. Also preferably, the heterogeneous catalyst is an immobilized catalyst, suggesting that it cannot leave the reaction zone. Immobilization of the heterogeneous catalyst can be achieved, for example, by incorporating the catalyst into the packing of the reaction zone.

The above-mentioned acidic catalyst may be an acidic resin, specifically an acidic ion exchange resin. The acidic resin may be any acidic resin capable of protonating the water and/or alcohol present in the process. The proton of the acidic functional group of this acidic resin can advantageously activate the alcohol to undergo a desired reaction. When such acidic resins are used, the water present in the process can advantageously be used both for activating and stabilizing such acidic resins. This is because acidic resins can swell considerably when in contact with water. When it dries, the carrier polymer matrix can become brittle and any broken pieces can escape from the cage holding them in the reaction zone with the packing. This suggests both stabilization and activation of the catalytic acid resin. The water also keeps the pores of the resin open and the acidic functional groups accessible.

Suitable examples of acidic resins are acidic resins based on sulfonated polystyrene. The latter acidic resin contains sulfonic acid (—SO ₃ H) groups. These acidic resins may be macroreticular (macroporous). Suitable commercially available examples of acidic ion exchange resins based on sulfonated polystyrene are Amberlyst 15 and Amberlyst 48.

Typically, a wide variety of catalysts may be used in the present invention. The nature of the catalyst is not essential to the present invention. For example, one or more of the catalysts described in the following references [1] to [9] may be used in the present invention. The disclosures of these references are incorporated herein by reference.

MgO-CeO ₂ as disclosed in reference [1] may be used as a catalyst in the present invention.

Organotin materials as disclosed in reference [2], for example, n-Bu ₂ Sn(OCH ₃ ) ₂ may be used as catalysts in the present invention.

Organocopper materials as disclosed in reference [3], for example Cu-AC [AC = activated carbon], can be used as catalysts in the present invention.

CeO ₂ as disclosed in reference [4] may be used as a catalyst in the present invention.

Reference [5] discloses the following. Various catalysts for the direct synthesis of DMC (dimethyl carbonate) have already been tested, including organometallic-alkoxy compounds, metal oxides, metal supported catalysts and ionic liquids. It is generally suggested that balanced acidic and basic properties play an important role in DMC synthesis for methanol activation. Most of the metal oxide studies deal with ceria or zirconia. The effect of crystal structure and morphology on activity is still debated. Ceria catalysts exhibiting nanorod, nanocube, octahedral and spindle-shaped morphologies exhibit various activities. In general, the observed trend is that mixed oxides often perform better than pure oxides. Therefore, the authors explored mixed oxides of modified ceria and zirconia, for example ceria, ceria-zirconia doped with H ₃ PO ₄ -functionalized ZrO ₂ , Al ₂ O ₃ , Fe ₂ O ₃ . One or more of the above catalysts as disclosed in reference [5] may be used as catalysts in the present invention. The CeO ₂ may be used in combination with at least one of Al, Zn, Fe, La, Y, Gd, Sm, Zr, Nd, Nb, and Ti.

Yttrium oxide Y ₂ O ₃ as disclosed in reference [6] can be used as a catalyst in the present invention.

Metal/activated carbon materials as disclosed in reference [7], such as Cu-Ni/AC and Ru-Fe/AC [AC = activated carbon], can be used as catalysts in the present invention.

Reference [8] discloses the following. ZnO-CeO ₂ in combination with 2-cyanopyridine can be used to remove the water formed during the reaction. The good catalytic activity is the combined effect of the crystal size of CeO ₂ and the optimal number of acidic and basic sites. A ZnO-CeO ₂ catalyst as disclosed in reference [8] may be used as a catalyst in the present invention.

Reference [9] discloses the following. Various types of catalysts such as organotin, copper-based catalysts, homogeneous and heterogeneous catalysts, organometallic complexes, phosphines, organic bases, metal oxides, acid-base bifunctional systems, zeolite-smectite catalysts and supported organic base catalysts was reported in DMC synthesis. One or more of the above catalysts as disclosed in reference [9] may be used as catalysts in the present invention.

References [1] to [9]

[1] Pawar et al., “Understanding the synergy between MgO-CeO ₂ as an effective promoter and ionic liquids for high dimethyl carbonate production from CO ₂ and methanol”, 2020, Chemical Engineering Journal 395, 124970.

[2] Ballivet-Tkatchenko et al., “Direct synthesis of dimethyl carbonate with supercritical carbon dioxide: characterization of a key organotin oxide intermediate”, Catal. Today., 115, 2006, pages 80-87.

[3] Merza et al., “The synthesis of dimethyl carbonate by the oxicarbonylation of methanol over Cu supported on carbon norit”, Catal. Lett., 145, 2015, pages 881-892.

[4] Tomishige et al., “Catalytic function of CeO ₂ in non-reductive conversion of CO ₂ with alcohols”, 2020, Materials Today Sustainability, 9, 100035.

[5] Daniel et al., “Discovery of very active catalysts for methanol carboxylation into DMC by screening of a large and diverse catalyst library”, 2020, New Journal of Chemistry, 44(16), pages 6312-6320.

[6] Sun et al., “Study of thermodynamics and experiment on direct synthesis of dimethyl carbonate from carbon dioxide and methanol over yttrium oxide”, 2020, Industrial and Engineering Chemistry Research, 59(10), pages 4281-4290.

[7] Arbelaez et al., “Transformation of carbon dioxide into linear carbonates and methane over Cu-Ni and Ru-Fe supported on pellets activated carbon”, 2020, Chemical Engineering Transactions, 79, pages 109-114.

[8] Challa et al., "Coupling of CH ₃ OH and CO ₂ with 2-cyanopyridine for enhanced yields of dimethyl carbonate over ZnO-CeO ₂ catalyst", 2019, Journal of Chemical Sciences 131(8), 86.

[9] Pawar et al., “Greener synthesis of dimethyl carbonate from carbon dioxide and methanol using a tunable ionic liquid catalyst”, 2020, Open Chemistry, 17(1), pages 1252-1265.

The invention is further illustrated in FIG. 1 .

1 , the liquid feed stream 1 comprising water, the liquid feed stream 2 comprising ethanol and the gaseous feed stream 3 comprising carbon dioxide are at different locations. It is sent to a reactive distillation column 4, where, as shown in FIG. 1, water is fed at the highest position and carbon dioxide is fed at the lowest position. Reactive distillation column 4 comprises a reaction zone 5 containing a heterogeneous catalyst capable of catalyzing the formation of organic carbonates (eg diethyl carbonate) from carbon dioxide and alcohols (eg ethanol).

The bottoms stream 7 from the reactive distillation column 4 contains the desired product, ie diethyl carbonate. The overhead stream (6) of the reactive distillation column (4) comprises diethyl carbonate, water, ethanol and carbon dioxide and is sent to a decanter (8) via a partial condensation step. Gaseous carbon dioxide is discharged from the decanter 8 through the top. In the decanter (8) two liquid phases are separated, wherein the upper phase comprising diethyl carbonate and ethanol is recycled to the reactive distillation column (4) as a first liquid stream (10) and the lower phase comprising ethanol and water is A second liquid stream (11) is sent to the distillation column (12). In distillation column 12, stream 11 is separated into a top stream 13 comprising ethanol, which stream is divided into an ethanol feed stream 2 and a bottoms stream comprising water removed from the process ( 14), it is recycled to the reactive distillation column (4).

Claims (10)

A process for preparing an organic carbonate comprising the step of contacting carbon dioxide with an alcohol in the presence of water and a catalyst in a reaction zone to produce the organic carbonate, wherein the organic carbonate is continuously removed from the reaction zone How to manufacture. Process according to claim 1 , wherein the alcohol is an aromatic C ₅ -C ₉ alcohol and/or an aliphatic C ₁ -C ₃₀ alcohol, preferably methanol or ethanol. Process according to claim 1 or 2, wherein the temperature is between 50 and 200 °C, preferably between 60 and 160 °C, more preferably between 70 and 140 °C. The process according to any one of claims 1 to 3, wherein the pressure is from 5 mbar to 10 bar, preferably from 10 mbar to 5 bar. 5 . The process according to claim 1 , wherein the reaction zone is part of a distillation column and the organic carbonate is continuously removed from the distillation column. 6. The method of claim 5, wherein carbon dioxide is contacted with an alcohol in the presence of water and a catalyst in a reaction zone of a first distillation column to produce a mixture comprising carbon dioxide, water, alcohol and an organic carbonate, wherein the organic carbonate is added to the first distillation column continuously removed from the first distillation column as a bottoms stream from, wherein the overheads stream from the first distillation column comprises carbon dioxide, water, alcohol and optionally organic carbonate. 7. The method of claim 6 wherein the overheads stream from the first distillation column comprises carbon dioxide, water, alcohol and organic carbonates;
the overheads stream is at least partially condensed and separated into a gas stream comprising carbon dioxide, a first liquid stream comprising organic carbonate and alcohol, and a second liquid stream comprising alcohol and water;
the separated first liquid stream comprising organic carbonate and alcohol is recycled to the first distillation column;
The separated second liquid stream comprising alcohol and water is fed to a second distillation column in which separation into a stream comprising alcohol and a stream comprising water is performed;
The separated stream comprising alcohol from the second distillation column is recycled to the first distillation column. 8. The method according to any one of claims 1 to 7, wherein the catalyst is an acid catalyst. The process according to claim 8 , wherein the acidic catalyst is an acidic resin, preferably an acidic resin based on sulfonated polystyrene. 10. The process according to any one of claims 1 to 9, wherein the catalyst is an immobilized heterogeneous catalyst.

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